Testing btrfs snapshots and git on ramdisk (tmpfs)

testing.md

These are my notes while testing.

Installing newer btrfs-tools

Ubuntu LTS 10.04 doesn't support removing btrfs snapshots. It can be fixed by installing newer btrfs.

cd /tmp
wget "http://se.archive.ubuntu.com/ubuntu/pool/main/b/btrfs-tools/btrfs-tools_0.19+20100601-3ubuntu3_i386.deb"
dpkg -i btrfs-tools_0.19+20100601-3ubuntu3_i386.deb

Creating the master git repository (on a flash drive):

mkdir -p /flash/disk0
cd /flash/disk0
git init
echo 'This is a test file.' > test.txt
git add test.txt
git commit -a -m 'Added initial test data.'

Initialising tmpfs

mkdir /ramdisks
mount -t tmpfs tmpfs /ramdisks
mkdir /ramdisks/raw /ramdisks/mnt

Creating images on ramdisk

dd if=/dev/zero of=/ramdisks/raw/disk0 bs=1M count=256

Initializing btrfs image

mkfs.btrfs /ramdisks/raw/disk0

Mounting btrfs image

mount -o loop /ramdisks/raw/disk0 /ramdisks/mnt/disk0

Cloning flash to the ramdisk

git clone /flash/disk0 /ramdisks/mnt/disk0/data

Creating snapshot

btrfsctl -s /ramdisks/mnt/disk0/snapshot/disk0-20120124-2149 /ramdisks/mnt/disk0/data

Removing snapshot

cd /ramdisks/mnt/disk0/snapshot && btrfsctl -D disk0-20120124-2149 . && cd -

For some strange reason this doesn't work:

# btrfsctl -D /ramdisks/mnt/disk0/snapshot/disk0-20120124-2149 /ramdisks/mnt/disk0/snapshot
ioctl:: Invalid argument

...or any of these -- although these are probably wrong anyway:

# btrfsctl -D disk0-20120124-2149 /ramdisks/mnt/disk0/data
ioctl:: No such file or directory
# btrfsctl -D /ramdisks/mnt/disk0/snapshot/disk0-20120124-2149 /ramdisks/mnt/disk0/data
ioctl:: Invalid argument
# btrfsctl -D disk0-20120124-2149 /ramdisks/mnt/disk0/snapshot
ioctl:: No such file or directory